Orthogonal Frequency Division Multiplexing (OFDM), a scheme for transmitting signals using multiple carriers, is a kind of multi-carrier modulation (MCM) that parallel-converts serial input symbols and modulates each of the parallel-converted symbols with multiple orthogonal sub-carriers before transmission. OFDM is widely applied to digital transmission technologies such as digital audio broadcasting (DAB), digital television (DTV), wireless local area network (WLAN), wireless asynchronous transfer mode (WATM), and so forth. In addition, OFDM is high in frequency efficiency and robust against multi-path fading as it transmits signals while maintaining orthogonality between multiple sub-carriers, thus making it possible to obtain high transmission efficiency.
However, an OFDM-based communication system may suffer from high PAPR due to the multi-carrier modulation. That is, since OFDM transmits data using multiple carriers, the final OFDM signal may experience a significant change in amplitude as the level of its amplitude is a sum of amplitudes of the multiple carriers. In addition, if the multiple carriers are equal even in phase, a level of their amplitudes may have a very large value. Therefore, the amplitudes may deviate from a linear operation range of a high-power linear amplifier, and the signals may undergo distortion when they pass through the high-power linear amplifier.
Meanwhile, a communication system using Multiple Input Multiple Output (MIMO) scheme has a very high channel capacity compared with a communication system using Single Input Single Output (SISO; or single-transmit/receive antenna technology) scheme. Accordingly, the next-generation wireless communication system tends to adopt MIMO (or multi-transmit/receive antenna technology) scheme, and intensive research is being carried out even on MIMO-OFDM scheme, which is a combined scheme of MIMO and OFDM. However, MIMO-OFDM scheme also suffers from high PAPR of signals.